This invention relates to a digital video encoder circuit and, more particularly, to a circuit for converting a digital chrominance signal from a display controller to an analog video signal according to a digital scheme.
In conventional systems such as a videotex system and a teletext system, character and graphic images are stored as digital data in an image memory, read out at a timing synchronized with raster scanning on a monitor CRT by a CRT (display) controller, and displayed on the CRT. Since color information data is normally read out as a digital waveform from these conventional systems, a special monitor for receiving a digital RGB signal is required. For this reason, when a standard television receiver capable of receiving only normal analog video signal serves as a monitor, a video encoder circuit is required to convert a digital chrominance signal into an analog video signal.
A conventional video encoder circuit is constituted by an analog circuit such as an analog IC.
When an analog video encoder IC is used, a large number of discrete peripheral components such as resistors, capacitors, inductors and delay lines are required, thus resulting in complicated assembly and adjustment and degrading reliability of the circuit itself. Electrical values of these components vary according to changes and deterioration over time. As a result, the electrical characteristics are undesirably degraded.